It depends entirely on cryptography . Not all cryptography is good in the long term, in the short term there is also a good cryptographic algorithm
Yes, it depends really on what coin. I witnessed several coins that comes and go. Only pump and dump and gone once the devs makes profit. LOng term coins are those that is back by several big group of people and having a foundation intended and over the develkopment of the said coin. It is supported by many and having many projects on the pipeline. TYou can see this on the top coins.